Using Antarctic ice-core records, we determine for each Antarctic Isotope Maximum (AIM) of Marine Isotope Stage 3 (MIS-3: ca. 28,000 to 59,000 years before present) the rates and durations of warming and atmospheric CO2 rise. We find that the AIM warming rates significantly decrease as the climate cools from early to late MIS-3. In contrast, the rate of CO2 rise during AIMs shows no significant trend across this interval. We further find that the AIM warming rate is not sensitive to Heinrich (H) events, contrasting with CO2, which rises for significantly longer time (compared to the temperature rise) during AIMs which coincide with H events. These distinct Antarctic temperature and CO2 responses to varying background climate and H events challenge the view that millennial-scale CO2 and Antarctic temperature changes are dominated by the same physical processes, suggesting an important contribution of low-to-mid-latitude processes to the CO2 rises.